In wellbores, patches or straddles are used for different purposes, such as for sealing a leak in a casing or a similar tubular structure, or for shutting off unwanted water/gas production from perforations. Patches are placed opposite the leak and expanded to abut the inside wall of the casing and thereby seal the leak. These patches often have to be run into the wellbore tubular and pass through restricted diameters within the wellbore. These restricted diameters are often referred to as “nipples”.
The patches are often expanded by means of a cone. When using a cone with a fixed diameter, the diameter of the cone is governed by the nipple restrictions which the patch must pass through prior to expansion and by the inner diameter of the patch once it has been expanded. The inner diameter of the patch after expansion is approximately the size of the wellbore tubular inner diameter minus twice the wall thickness of the patch. There are some tolerances which must be taken into account during expansion and contraction due to the elastic relaxation of the patch after expansion.
In addition, there are many cases where a patch is required later on in the lifespan of the well (possibly years) below a patch which has been previously set                a so-called patch through patch solution. In these cases, the inner diameter of the patch previously set may well be smaller than the nipple restrictions within the well.        
In addition, well bores may be completed by means of a well tubular shallower within the well with a smaller inner diameter than the wellbore tubular in which the patch needs to be set.
In existing cases, in order to pass an earlier patch or restriction with a cone, the cone may be made expandable, which makes demands on the tool and increases the complexity of the tool and thus the cost as well as the risk of tool failure.